In Search of the Energy-Efficient Family Car

Buying a car just isn't as easy as it used to be, especially when you know just enough about alternative-fuel-source vehicles to make that decision very difficult. As my husband and I debate the merits and faults of energy-efficient cars (as the end date of his leased Prius looms in the background), I feel as though we must make a smart choice that is right for us and right for the planet. Perhaps you relate to such a quest for the perfect car that balances safety, comfort, fuel efficiency, and style.

When I entered this decision tree of what fuel-efficient car to buy, I initially thought that an electric vehicle (EV) would be the simple solution. EVs, which run on chargeable batteries, seem to make sense for our family. We live in an urban area and rarely take long trips requiring a long charge. We'll just plug the car in at night and stop using petroleum that pollutes the air. Right?

Not quite. As I started discussing the decision with my MEMS colleagues (all with their EEs and MEs), I quickly learned that it's not that simple. First, the biggest limitation is the battery itself. The energy-to-weight ratio for EVs is quite abysmal compared with gasoline. Up to one-third of an EV's total weight can be attributed to the battery pack alone, and most of the batteries hold a charge for a few hundred miles at best. That's a deal breaker for many.

Tesla appears to be the only EV company that is seriously attacking the battery issue. Its CTO has said battery energy density is improving about 7 percent a year. This clearly shows that his company understands one of the biggest roadblocks to EV adoption. Tesla has designed a beauty of a lightweight car that is chock full of MEMS/sensors and showcases an iPad-like dash between the passenger and driver. Plus it has two trunks; that is just so cool. (It's the reason my 12-year-old daughter insists we buy a Tesla.)

Until we have cars that run on solar panels, energy is never free. Even if you decide to buy a Tesla, you have to think about where the energy is generated to recharge the battery every night. For me in Pittsburgh (and for most of the Northeast), the source is typically coal. Uh, oh. That means I would deplete more fossil fuels and release more greenhouse gases if I bought an EV. Another important issue is the disposal of heavy-lead lithium batteries. Some EVs need to replace their batteries after three years. So if you are the average American who holds on to a car for five years, you'll need to dispose of (and pay for) two batteries and consider the environmental impact of that decision.

Let's face it -- the batteries for EVs (and for most consumer electronics) are still inefficient. Here's where my MEMS brain starts to activate and I start thinking about energy harvesting. Can't we find ways through MEMS to harvest the car's vibrations at least to power its electronics?

I bet the folks at MicroGen Systems are already looking into this. I actually know of a few more companies (big and small) that are looking into ways to make vehicles smarter and energy efficient from the get go through a combination of MEMS and sensors. Examples include energy harvesters in the tire that capture the vibrations and power the tire-pressure monitoring system, as well as sensors embedded into an engine to maximize fuel efficiency. Take it one step further, and HVAC monitoring systems managed by an in-car sensor network could keep passengers comfortable as the vehicle passes through varying daylight and temperature conditions. MEMS will make this happen.

I guess I will have to wait until there's smarter battery technology that recharges an EV by green energy. In the meantime, I'll be asking my local car dealer how many MEMS and sensors are inside the vehicle. The car with the most MEMS wins.

The effort required to obtain a charging station at a place of employment is certainly not trivial by any stretch. In addition there is always the probability that some others would choose to park in that spot, either to use the charging connection or else just because they could. Perhaps it would be easier to do in some prts of the country and at some employers, but my preference has been to work at the smaller organizations that are not so very gifted with all kinds of resources. Besides all of that, my EV would still need charging on those days when I don't go to work. In addition it is not clear that there would be enough solar electricity available from a reasonably priced array to charge an EV in the time of available sunshine. And in this corner of michigan we often have days that would not power solar charging at all. So while solar generated electricity is probably a good idea in principle, it is probably not the best choice for charging up a car.

For recharging an EV from a solar charger, the big challenge is that most solar chargers work poorly in the dark. And given that the classic work schedule has one away from home doing work during the sunshine hours, that winds up being a problem, and I don't see an easy way around it , except to have two battery packs and charge them on alternate days. BUt that is both expensive and a lot of work.

You are asking the right general question, you aren't using the best tools to analyze the answer.

1) I admire you are looking at EVs for a family car, but, be aware, that the technology isn't ready for main stream, you when you buy an EV are being an Early adopter, and need to be a savvy user. Buying an EV car today is much like buying a personal computer in 1983, you need to be Nerd Friendly and willing to play with the technology.

2) The measures to analyze a car isn't Curb weight but you probably want to consider Grams CO2/KM or Levelized Cost/ KM. Why do you care what the weight is? Are you going to pick it up? Weight matters within the same format and type, it matters less comparing an EV to a hybrid to a ICE engine. EVs perform great on crash because they are heavy, that low battery keeps them from turning over and handle momentum.

3) By 2020, electrics will have fully invaded the market, but, right now EVs are closer to the 1930's then the 1980's. That means you have to consider Daily Range requirements and then consider Weekend range requirements and then family trips. When i was a kid, my parents would buy tiny little cracker box cars, Mom had a Fiat 128 and Dad drove a Toyota Corolla. You could fit 2 adults and 3 kids in the back but for trips out of town, they would rent a car for the holiday, usually a station wagon, so we could take the dog, coolers, luggage, etc.. With an EV, you may need to do that for awhile.

4) Level 3 chargers are growing fast, right now what is a "Adventure" figuring out how to go cross country on electric, is rapidly turning into a task equivalent to driving a diesel or propane car. You will need a map of the stations, but you are unlikely to find yourself range challenged. http://www.teslamotors.com/supercharger http://www.afdc.energy.gov/locator/stations/results?utf8=%E2%9C%93&location=&filtered=true&fuel=ELEC&owner=all&payment=all&ev_dc_fast=true&radius_miles=5 THere are 181 Level 3 chargers nationwide, soon there will be more. What you need is enough range for daily driving

5) The Hybrids are the gateway drug to an EV, consider a Prius V mini wagon, or a

Toyota Highlander Hybrid or a plug in Prius,

6) WHat powers your grid drives your carbon loads, but you can buy power from clean sources. In DC, we can buy electricity from Clean Currents, what prevents you from

opting for Clean electricity? Also, you can get a 2 KW solar array and go to generating your own clean power for the car.

If you want a big family van or 7 passenger car, the EV's aren't really there at good price points, but, if you can delay 2 years or look at a Leaf or FIT EV or Spark EV as a supplemental car, the market is expanding fast.

Hey Brooks, I agree that practical EVs will be available long before fossil fuels give out. It will happen slowly. At some point fossil fuels will become so expensive that EVs won't seem so dear. Plus, EV technology developments will bring down the cost of EVs.

My impression is that the energy harvesting suspension tale has been rather completely debunked. On most roads there is just not enough suspension travel to generate enough power to be worth the effort. Of course, gravel roads with the washboard potholes would be the exception, but most folks avoid those where there is any other choice available. All that you need to do to prove that is put a temperature monitor on a shock absorber and then wrap it with insulation, and watch the temperature rise as you drive. Not enough energy to be worth the expense of collecting it, given the small amount of power that the alternators use. And in addition, there would be a much smaller amount to recover when stuck in slowly moving city traffic.

Likewise, regenerative braking would not work out very well in typical slow city driving, although it could be worthwhile in a more suburban scene.

For any energy harvesting scheme to be worthwhile, the amount of energy available must be adequate, other wise, just because it can be done does not mean that it is worth doing.

I had a similar experience, Hank-4. I learned to drive on a 1965 Bel Ait station wagon with no AC, no power steering and a stick shift. It was tough to parallel park and tough to learn on, but after that, every car seemed easy to drive.

Wilkliam K, I like the idea of adding insulation to cut donw on the need for air conditioning. The insulation would be a one-time cost, and the savings on fuel would probably pay for it over and over. I was fine without air conditioning when I lived in Michigan. Now that I'm in New Mexico, it's a different story.

Right you are, William K. I managed to drive a 1965 Ford Country Sedan (station wagon) with a 390 CID engine, A/C, and NO power steering. It wasn't much fun to parallel park but once you were moving, steering wasn't really an issue.

A power steering system would certainly not be a requirement for a vehicle under 2000 lbs GVW (maybe for a HC driver). The line you always get from manufacturers re power steering is ".... FWD vehicles are harder to steer and need power steering....." Many years ago I drove a vehicle w/FWD and NO power steering. I couldn't really tell much difference between it and a RWD vehicle, as far as sterring difficulty under normal driving conditions. Anyway, all the extra compnents turn out to be additional failure points.

Industrial workplaces are governed by OSHA rules, but this isn’t to say that rules are always followed. While injuries happen on production floors for a variety of reasons, of the top 10 OSHA rules that are most often ignored in industrial settings, two directly involve machine design: lockout/tagout procedures (LO/TO) and machine guarding.

Load dump occurs when a discharged battery is disconnected while the alternator is generating current and other loads remain on the alternator circuit. If left alone, the electrical spikes and transients will be transmitted along the power line, leading to malfunctions in individual electronics/sensors or permanent damage to the vehicle’s electronic system. Bottom line: An uncontrolled load dump threatens the overall safety and reliability of the vehicle.

While many larger companies are still reluctant to rely on wireless networks to transmit important information in industrial settings, there is an increasing acceptance rate of the newer, more robust wireless options that are now available.

To those who have not stepped into additive manufacturing, get involved as soon as possible. This is for the benefit of your company. When the new innovations come out, you want to be ready to take advantage of them immediately, and that takes knowledge.

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